A phosphate coating is generally deposited on the surface of a metal material so as to serve as a lubricating base for cold forging, a paint base or the like, but a phosphate coating is hard to be deposited on the surface of a stainless-steel material by a conventional immersion method. For this reason, in many cases, oxalate treatment is applied to a stainless-steel material so as to deposit an oxalate coating thereon. This oxalate coating, however, has a deteriorated property as comparison with a phosphate coating, and therefore there is a demand for a method of depositing a phosphate coating even on a stainless steel material. In consideration of this, the present applicants have developed a technique to deposit a phosphate coating on a stainless steel material by electrolysis treatment.
This electrolysis treatment enables deposition of a phosphate coating, but the applicants encountered another problem of the necessity to achieve uniform and high-speed deposition of a coating. This is a critical issue in light of the application of this technique to a manufacturing step in cold forging process, or the like.
Accordingly, it is an object of the present invention to provide a phosphate coating apparatus and a chemical conversion coating apparatus that are capable of achieving uniform and high-speed deposition of a coating.